On 12 January 2016, the European Food Safety Authority (EFSA) Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF) issued a scientific opinion dealing with the risk assessment of tetraethyl orthosilicate (TEOS) and hexamethyldisilazane (HMDS). It has found their mixture safe for use in food contact materials.

Here are more details for the two chemicals:
Tetraethyl orthosilicate (TEOS), Chemical Abstract Service (CAS) No 78-10-4, Food Contact Material (FCM) substance No 01013;
Hexamethyldisilazane (HMDS), CAS No 999-97-3, Ref. No 18455 and FCM substance No 01014.

According to the applicant, the two substances are used together as a chain extender for polyethylene terephthalate (PET) to increase the molecular weight of the polymer after recycling.

The CEF Panel concluded the mixture composed of TEOS and HMDS does not raise a safety concern for the consumer if it is used at up to 0.12% (w/w) for the production of recycled PET.